JP2008060017A - Microwave utilization apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microwave utilization apparatus having a compact power supply circuit to be mounted easily without a large-scale insulating structure and radio shielding structure. <P>SOLUTION: DC voltage obtained by a rectifying bridge 19 and a rectifying filter smoothing circuit 22 is transmitted in electric power at high frequency by switching operation using a power MOSFET 33 and a control IC 30 while a microwave generating device is operated in a floated state by an insulation transformer 24, and electric power is supplied to the microwave generating apparatus while an input current waveform is kept in a sine wave. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The microwave utilization apparatus of the present invention relates to a microwave application apparatus such as a heating apparatus that uses dielectric heating as typified by a microwave oven or illumination that irradiates a light emitter with a microwave to obtain a light source.

  Conventionally, this microwave utilization device has a solid-state high-frequency oscillator using a semiconductor and a multi-stage power amplifier that amplifies the solid-state high-frequency oscillator, and a stabilized power supply circuit that supplies power to the individual high-frequency oscillator and a multi-stage power amplifier. A rectifying / smoothing circuit for supplying power is provided individually (see, for example, Patent Document 1).

FIG. 13 is a circuit diagram of a power supply unit of a conventional microwave utilization apparatus. The voltage of the commercial power source 1 is half-wave rectified by a rectifying / smoothing circuit 20 for half-wave rectification, and then the voltage is stepped down by resistance division to supply power from the output terminal 21 to the amplifier. In addition, the power to the exciter is stabilized by the constant voltage power supply circuit 23 via the transformer 24 and supplied from the output terminal 22. Therefore, power was supplied to the amplifier and exciter from the commercial power supply with two circuits.
JP-A-53-10942

  However, in the above-described conventional invention, the rectifying / smoothing circuit for supplying power to a plurality of stages of power amplifiers is obtained by rectifying and smoothing a commercial power source. Therefore, the direction end of the output terminal 20 is directly supplied to the microwave utilization apparatus. The problem at this time will be described taking a microwave oven as an example.

  A metal oven cavity (same potential as the body metal housing) for storing food is electrically connected to the microwave device, and when the user touches the housing, the end of the commercial power supply is touched, resulting in an electric shock. That is indispensable. In order to avoid this, it is necessary to combine the microwave utilization device and the oven cavity while ensuring a predetermined insulation, and it is also necessary to have a radio wave shielding structure for preventing leakage of the microwave. It becomes a thing.

  The present invention solves the above-described conventional problems, and provides a power supply circuit as a configuration for insulating a commercial power supply from a microwave utilization device, so that it is compact and mountable without a large-scale insulation configuration and radio wave shielding structure. The microwave utilization apparatus provided with the power supply circuit excellent in this is provided.

  In order to solve the above-mentioned conventional problems, the microwave utilization apparatus of the present invention is provided with an insulating transformer in the subsequent stage of the commercial power supply.

  The microwave utilization apparatus of the present invention is electrically insulated by a transformer after the commercial power supply, and the microwave utilization apparatus is completely floating, so that a large-scale insulation structure and radio wave shielding are provided between the commercial power supply and the microwave utilization apparatus. It is an object of the present invention to provide a microwave utilization device having a compact power supply circuit that has no structure and excellent mountability.

  According to a first aspect of the present invention, an oscillator that generates a microwave, an amplifier that amplifies the microwave generated by the oscillator, an insulated power supply circuit that supplies power to the amplifier, and a microwave that is amplified by the amplifier are radiated. The amplifier includes a semiconductor element made of a compound semiconductor having a band gap of 3 eV or more, and the power supply circuit includes an isolation transformer after the commercial power supply, thereby electrically floating the commercial power supply and the oscillator. Therefore, it is not necessary to provide an insulating structure or a radio wave shielding structure, and thus a microwave utilization device with a simple configuration can be obtained.

  According to a second aspect of the present invention, an oscillator that generates a microwave, an amplifier that amplifies the microwave generated by the oscillator, an insulated power supply circuit that supplies power to the amplifier, and a microwave that is amplified by the amplifier are radiated. The amplifier includes a semiconductor element made of a compound semiconductor having a band gap of 3 eV or more, and the power supply circuit includes an isolation transformer after the commercial power supply and rectifies and smoothes the secondary output of the isolation transformer By doing so, the power source supplied to the oscillator can be changed to a DC power source, and an amplifier composed of a compound semiconductor can be efficiently driven to output a microwave from the radiating portion. A high-performance microwave utilization device can be obtained.

  A third invention includes an amplifier that amplifies the microwave generated by the oscillator, an insulating power supply circuit that supplies power to the amplifier, and a radiation unit that radiates the microwave amplified by the amplifier. Including a semiconductor element made of a compound semiconductor having a band gap of 3 eV or more, and the power supply circuit includes an insulation transformer in the subsequent stage of the commercial power supply and rectifies and smooths the secondary output of the insulation transformer as a DC-DC converter By making the output variable, the power supplied to the oscillator can be changed to a direct current power source, and an amplifier composed of a compound semiconductor can be efficiently driven to output a microwave from the radiating section, and the intensity of the microwave can be varied freely. Thus, it is possible to obtain a microwave utilizing apparatus having a fine heating pattern and high performance and excellent heating controllability.

  According to a fourth aspect of the present invention, a reactor is provided in the high power current line in the second or third aspect of the invention, thereby increasing the current common angle of the capacitor input waveform having a large current harmonic component, thereby increasing the current harmonic. The input current waveform with less components can be improved, and high-order harmonic components can be removed from the power distribution system, so the input voltage supplied to peripheral devices can be reduced to a sinusoidal voltage with little distortion. The EMC problem which arises from the power supply distortion of an apparatus can be avoided, and a high performance microwave utilization apparatus can be obtained regarding EMC.

  According to a fifth aspect of the present invention, there is provided an oscillator for generating a microwave, an amplifier for amplifying the microwave generated by the oscillator, an insulated power supply circuit for supplying power to the amplifier, and a microwave amplified by the amplifier. The amplifier includes a semiconductor element made of a compound semiconductor having a band gap of 3 eV or more, and the power supply circuit has a PFC function and a DC-DC converter function with variable output at the subsequent stage of the commercial power supply and power at a high frequency. It can be transmitted to the secondary side of the transformer, the input current waveform can be made sinusoidal, the EMC problem caused by the power supply distortion of the peripheral equipment can be avoided, and the high-performance microwave utilization device for EMC Can be provided.

  In the sixth invention, the isolation transformer of the power supply circuit is provided with a center tap on the secondary side and can output full-wave rectified and smoothed with two diodes and one capacitor to output DC voltage. Therefore, it is not necessary to give excessive responsibilities and excessive specifications to these parts, and it is possible to provide a low-cost and compact microwave utilization apparatus.

  Hereinafter, a microwave generator according to an embodiment of the present invention and a microwave processing apparatus including the microwave generator will be described with reference to the drawings using a microwave oven as an example. Note that the present invention is not limited to the present embodiment.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a microwave oven according to an embodiment of the present invention. As shown in FIG. 1, a microwave oven 6 according to the present embodiment includes a microwave generator 3 and a housing 7. In the housing 7, antennas A1 and A2 are provided. The housing 7 is grounded.

  The microwave generation unit 3 includes a power supply circuit 2, a microwave generation unit 3, and a microwave amplification unit 4. The microwave generator 3 is connected to a commercial power source 1 (not shown in the figure) through a plug 8.

  In the microwave generator 5, the power supply circuit 2 converts the AC voltage supplied from the commercial power supply 1 into a variable voltage and a DC voltage, applies the variable voltage to the microwave generator 3, and supplies the DC voltage to the microwave amplifier 4. To give.

  The microwave generator 3 generates a microwave based on the variable voltage supplied from the power supply circuit 2. The microwave amplifying unit 4 operates with a DC voltage supplied from the power supply circuit 2, amplifies the microwave generated by the microwave generating unit 3, and an antenna A 1 provided in the casing 7 Give to A2. Thereby, microwaves are radiated from the antennas A <b> 1 and A <b> 2 in the housing 7. Details of configurations and operations of the power supply circuit 2, the microwave generation unit 3, and the microwave amplification unit 4 will be described later.

  2 is a schematic side view of the microwave generation unit 1 constituting the microwave oven 1 of FIG. 1, and FIG. 3 is a diagram schematically showing a circuit configuration of the microwave generation device 1 of FIG. The microwave generation unit 3 in FIG. 2 includes heat radiating fins 31, a circuit board 32, and a cover member IM2. A microwave generator 3 is formed on the circuit board 32. The circuit board 32 is provided on the heat radiation fin 31 in the cover member IM2. The microwave generator 33 is composed of a circuit element such as a transistor, for example.

  The microwave amplifying unit 4 in FIG. 2 includes heat radiating fins 41, a circuit board 42, and a cover member IM3. The circuit board 42 is provided on the heat radiation fin 41 in the cover member IM3. The microwave generator 3 and the microwave image antinode 4 are coupled by a coaxial cable CC1. Similarly, the microwave amplifying unit 4 and the antenna are coupled by coaxial cables CC2 and CC3.

  As shown in FIG. 3, the output terminal of the microwave generation unit 3 is input to the microwave amplification unit 4 via the coaxial cable CC1. The microwave amplifying unit 4 has two parallel amplifier paths and outputs one amplified high-power microwave output to the antenna A1 via the coaxial cable CC2. The other high-power microwave output is output to the antenna A2 via the coaxial cable CC3 (details of the microwave generation unit 3 and the microwave amplification unit 4 will be described with reference to FIG. 4). The antennas A1 and A2 are provided in the housing 7 of the microwave oven 6.

  An insulation transformer 13 is arranged at the subsequent stage of the commercial power source 1 to insulate it from the subsequent circuits. The power supply circuit 2 is formed of one diode. Only the positive side of the sine wave voltage is detected. The output terminal outputs Vdd and Vss voltages and uses them as circuit drive voltages for the microwave generator 3 and the microwave amplifier 4. In terms of waveform, a pulsating voltage is applied every half of the power supply frequency.

  Here, an insulation transformer 13 is arranged immediately after the commercial power source 1 and the secondary side is electrically separated from the potential of the commercial power source 1 and is in a floating state. The output Vss of the insulation transformer 13 is connected to the ground to the same potential as the casing 7 of the microwave oven 6.

  With this configuration, the commercial power source 1 and the microwave generator 4 can be electrically floated, so that it is not necessary to have an insulating structure or a radio wave shielding structure, and a microwave utilization device with a simple configuration Can be obtained.

(Embodiment 2)
As shown in FIG. 4, the output terminal of the microwave generation unit 3 is connected to the input terminal of the amplifier 9 via a line formed on the circuit board 32, a coaxial cable CC <b> 1, and a line formed on the circuit board 42. Yes. The output terminal of the amplifier 9 is connected to the input terminal of the power distributor 18 via a line formed on the circuit board 32. The power distributor 18 distributes the microwave input from the amplifier 9 via the line and outputs it.

  The two output terminals of the power distributor 18 are connected to the input terminals of the amplifiers 10 and 11 through two branch lines formed on the circuit board 42.

  An output terminal of the amplifier 6 is connected to one end of the coaxial cable CC <b> 2 via a line formed on the circuit board 42. The other end of the coaxial cable CC2 is connected to the antenna A1. The antenna A1 is provided in the housing 7 of the microwave oven 6.

  The output terminal of the amplifier 11 is connected to one end of the coaxial cable CC3 through a line formed on the circuit board 42. The other end of the coaxial cable CC3 is connected to the antenna A2. The antenna A2 is provided in the housing 7 of the microwave oven 6.

  Here, an insulation transformer 13 is arranged immediately after the commercial power source 1 and the secondary side is electrically separated from the potential of the commercial power source 1 and is in a floating state. The output of the isolation transformer 13 is full-wave rectified by a full-wave rectification bridge 19 and converted to a DC voltage by the choke coil 14 and a smoothing capacitor. The upper line is supplied as the Vdd voltage of the three amplifiers of the microwave amplifying unit 4 as the circuit voltage Vdd potential. On the other hand, the lower line is supplied as the Vss potential as Vdd voltages of the three amplifiers of the microwave amplifying unit 4. Vss is connected to the earth ground having the same potential as the casing 7 of the microwave oven 6.

  The switching regulator 17 that is supplied with electric power from the potentials Vdd and Vss can supply a stabilized Vcc voltage to the microwave oscillator 16 of the microwave generator 3 to generate a very stable microwave reference signal.

  With this configuration, the commercial power source 1 and the microwave generator 4 can be electrically floated, so that it is not necessary to have an insulating structure or a radio wave shielding structure, and a microwave utilization device with a simple configuration Can be obtained. Moreover, since microwaves are continuously output with complete direct current, power efficiency and utilization are extremely high.

  Here, an insulation transformer 13 is arranged immediately after the commercial power source 1 and the secondary side is electrically separated from the potential of the commercial power source 1 and is in a floating state. The output Vss of the insulation transformer 13 is connected to the ground to the same potential as the casing 7 of the microwave oven 6.

  With this configuration, the commercial power source 1 and the microwave generator 4 can be electrically floated, so that it is not necessary to have an insulating structure or a radio wave shielding structure, and a microwave utilization device with a simple configuration Can be obtained.

(Embodiment 3)
FIG. 5 is a block diagram of a microwave utilization apparatus according to the third embodiment of the present invention. The commercial power source 1 is full-wave rectified by the rectifier bridge 19 and converted into a unidirectional pulsating flow. The output of the rectifying bridge 19 is converted to DC by the rectifying filter smoothing circuit 22. The DC-DC converter 23 including the insulation transformer 24 in the power transmission path performs DC-DC conversion and outputs three voltages Vdd, Vcc, and Vss as potentials. The detailed configuration, operation, and effects after the microwave generation unit 3 are the same as those in FIG.

  FIG. 6 shows details of the DC-DC converter 23. First, the commercial power source 1 is converted into a unidirectional pulsating flow by the rectifying bridge 19. The output is converted to DC by a rectifying filter smoothing circuit 22 including a choke coil 25 and a smoothing capacitor 26 and output to a DC-DC converter 23. Here, a tank resonance circuit composed of a leakage inductance of the resonance capacitor 27 and the isolation transformer 24, and a switching means in which a power MOSFET 33 and a FWD 24 connected in series are configured in parallel. A signal line for controlling the on / off of the power MOSFET 33 so as to convert the DC voltage into a DC voltage of another potential is TL1. The control IC 30 performs the function of sending the PWM signal to the power MOSFET 33 using the TL1 signal.

  The secondary side of the isolation transformer 24 is half-wave rectified by a diode 28 and a smoothing capacitor to obtain Vdd and Vss as DC voltages. The switching regulator 17 creates a more stabilized voltage Vcc from the Vdd and Vss. Since how Vdd, Vss, and Vcc are used to generate microwaves has already been described in detail with reference to FIG. 4, a description thereof is omitted here.

  The operation of the DC-DC converter 23 will now be described using the timing chart of FIG. First, when the gate signal Vg of the power MOSFET 33 is turned on (in the case of [1]), the current increases monotonously through the leakage inductance of the isolation transformer 24 (in the case of [2]). At the timing of turning off the gate signal Vg (in the case of [3]), the current flows toward the resonance capacitor 27 and resonates with the C component and the L component. This is a so-called resonance phenomenon in which electric charges are accumulated in or discharged from the resonant capacitor 27, and the voltage Vsd is excited (in the case of [4]). Further, when Vsd touches the negative side, the current of the resonant capacitor 27 flows in the reverse direction via the FWD 34 (in the case of [5]). This is repeated to charge the secondary smoothing capacitor 29 with the leakage inductance of the insulating transformer 24 as if it were an energy pump.

  This switching frequency is set to a high frequency of 50 to 100 kHz. Therefore, the isolation transformer 24 can be very miniaturized.

  On the other hand, in order to achieve DC stability of the output voltage, the output voltage information must be returned to the control IC 30 and negative feedback controlled between the reference potential and a constant value control. Therefore, the output voltage is divided by the resistor 38 and the resistor 39, the signal is voltage-frequency converted by the VF converter 35, insulated by the photocoupler 37, and the pulse train signal is fed back to the control IC 30. The control IC 30 has a frequency-voltage conversion function, and controls the output voltage to a constant value by absorbing the difference between the converted voltage signal and the reference voltage signal.

  The DC voltage is controlled by the pulse width of Vg, the pulse width τ is decreased when it is desired to lower the output DC voltage, and the pulse width is increased when the output DC voltage is desired to be increased. As shown in FIG. 8, when the duty ratio of the horizontal axis τ / T, the vertical axis, and the output voltage are used, the output voltage can be varied substantially in a relationship proportional to the duty ratio.

With this configuration, the commercial power source 1 and the microwave generator 4 can be electrically floated, so that it is not necessary to have an insulating structure or a radio wave shielding structure, and a microwave utilization device with a simple configuration Can be obtained.

(Embodiment 4)
In Embodiments 2 and 3, since the output voltage is completely DC, current must flow only near the peak of the commercial power supply waveform. This input current waveform is called a capacitor input waveform. FIG. 10A shows the waveform. This capacitor input waveform contains many high-order harmonic components in the current. When such a device is used as a load, the waveform of the voltage itself supplied from the switchboard is also affected by the high-order current, and has a negative effect on other devices.

  In view of this, the high-order current component is restricted in numerical values even in technical regulations, and clearing this restriction is an urgent issue for devices that are DC smoothed using a large electrolytic capacitor.

  Therefore, as a countermeasure, a large L element of about 10 mH called a reactor is inserted into the line to widen the common angle through which the input current flows to avoid exceeding the standard value. Specific examples thereof are shown in FIGS. 9A and 9B. In FIG. 9A, a reactor is inserted in the line before the rectifying bridge. (B) inserts a reactor in the line after the rectifier bridge.

  As for the effect, it cannot be said which is better and is almost equivalent. As shown in FIG. 9 (b), the phase is clearly advanced, but the same angle is widened to satisfy the regulation.

  As described above, in the microwave generator having the capacitor input waveform, it is possible to provide a device in which current harmonics can be suppressed by inserting a reactor and an EMC problem to other devices does not occur.

(Embodiment 5)
Although basically the same as the configuration of the third embodiment, the operation algorithm of the control IC 30 is different. The leakage inductance energy of the insulating transformer 24 is stored at a frequency of 50 to 60 kHz over the power cycle, and the energy is stored in the secondary smoothing capacitor 29.

  The feature here is that the peak value of the switching current Is is controlled based on the product VinVout of the input voltage Vin and the output voltage Vout.

  As a result, when the input voltage is low, Vin is reduced and Is is reduced. Conversely, when the input voltage is high, VinVout increases and Is increases. The output voltage is stabilized because it is based on VinVout.

  Therefore, the input current waveform is very close to a sine wave without using a large passive component such as a reactor. It is possible to provide a high-quality microwave generator that is lightweight and compact and is not affected by harmonic current.

(Embodiment 6)
In the third and fifth embodiments, a transformer having an intermediate tap on the secondary side, such as the insulating transformer 29, is used. The secondary part consists of two diodes and one smoothing capacitor. In the case of one output polarity, the charge is charged in the smoothing capacitor 29 through the diode 28, and in the other polarity, the charge is charged in the smoothing capacitor 29 through the diode 40. Since the power is charged and consumed by both groups, it is possible to provide a microwave generator that has good power utilization and a smoothing capacitor that is correlated with ripples but can be used in a small size and has excellent cost performance.

  As described above, the microwave utilization apparatus according to the present invention supplies the commercial power source and the microwave generator electrically to the microwave unit and the microwave amplifier in order to supply the voltage converted into the commercial power source using the insulation transformer. Therefore, it is not necessary to provide an insulating structure or a radio wave shielding structure, and a microwave utilization device with a simple configuration can be obtained. Therefore, it is possible to reduce the cost of the heating source used in the heating apparatus and the garbage processing machine using dielectric heating as typified by a microwave oven and to greatly reduce the storage space. In addition, because of its compactness, it is possible to provide a microwave application apparatus such as illumination for irradiating a light emitter with a microwave to obtain a light source at a more reasonable size.

Simplified block diagram of the microwave utilization apparatus of the present invention Structure diagram of microwave generator of the present invention The simplified block diagram of the microwave utilization apparatus in the 1st Embodiment of this invention The circuit diagram of the microwave utilization apparatus in the 2nd Embodiment of this invention The simplified block diagram of the microwave utilization apparatus in the 3rd Embodiment of this invention The circuit diagram of the microwave utilization apparatus in the 3rd Embodiment of this invention Timing chart of each part waveform of microwave using device in third embodiment of the present invention Input / output characteristic diagram of microwave utilization apparatus according to third and fifth embodiments of the present invention (A) Arrangement configuration diagram of reactor of microwave utilization apparatus in the fourth embodiment of the present invention (b) Arrangement configuration diagram of reactor of different arrangement (A) It is explanatory drawing for demonstrating the effect of the reactor of the microwave utilization apparatus in 4th Embodiment of this invention, Comprising: When there is no reactor, ie, explanatory drawing of the waveform before improvement (b) If there is, that is, an explanatory diagram of the improved waveform The principal part circuit diagram of the insulation transformer of the microwave utilization apparatus in the 5th Embodiment of this invention Principle explanatory drawing of the microwave utilization apparatus in the 6th Embodiment of this invention Circuit diagram of power supply unit of conventional microwave application device

Explanation of symbols

1 Commercial power supply 2 Power supply circuit 3 Oscillator (microwave generator)
4 Amplifier (Microwave amplification equipment)
6 Microwave oven 19 Rectifier bridge 23 DC-DC converter circuit 24 Insulation transformer

Claims (6)

A microwave generator for generating microwaves,
An oscillator that generates microwaves;
An amplifier for amplifying the microwave generated by the oscillator;
An insulated power supply circuit for supplying power to the amplifier;
A radiating unit that radiates microwaves amplified by the amplifier;
The microwave generator according to claim 1, wherein the amplifier includes a semiconductor element made of a compound semiconductor having a band gap of 3 eV or more, and the power supply circuit includes an insulation transformer in a stage subsequent to a commercial power supply. A microwave generator for generating microwaves,
An oscillator that generates microwaves;
An amplifier for amplifying the microwave generated by the oscillator;
An insulated power supply circuit for supplying power to the amplifier;
A radiating unit that radiates microwaves amplified by the amplifier;
The amplifier includes a semiconductor element made of a compound semiconductor having a band gap of 3 eV or more, and the power supply circuit includes an insulation transformer in a subsequent stage of a commercial power supply and rectifies and smoothes the secondary output of the insulation transformer. A feature of the microwave generator. A microwave generator for generating microwaves,
An oscillator that generates microwaves;
An amplifier for amplifying the microwave generated by the oscillator;
An insulated power supply circuit for supplying power to the amplifier;
A radiating unit that radiates microwaves amplified by the amplifier;
The amplifier includes a semiconductor element made of a compound semiconductor having a band gap of 3 eV or more, and the power supply circuit includes an insulation transformer in a subsequent stage of a commercial power supply and rectifies and smooths the secondary output of the insulation transformer. A microwave utilization apparatus characterized in that the output is variable by a DC-DC converter. The microwave utilization apparatus according to claim 2 or 3, wherein a reactor for a high power current line is provided. A microwave generator for generating microwaves,
An oscillator that generates microwaves;
An amplifier for amplifying the microwave generated by the oscillator;
An insulated power supply circuit for supplying power to the amplifier;
A radiating unit that radiates microwaves amplified by the amplifier;
The amplifier includes a semiconductor element made of a compound semiconductor having a band gap of 3 eV or more, and the power supply circuit has a PFC function and a DC-DC converter function with variable output at the subsequent stage of the commercial power supply, and supplies power at a high frequency to the secondary of the transformer. A microwave device that transmits to the side. The microwave utilization device according to any one of claims 3 to 5, wherein the transformer of the power supply circuit has a center tap on the secondary side and performs DC conversion with two diodes and one capacitor.

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